Abstract Behavior setting theory was developed by Roger Barker to explain small-scale social systems, as well as the study of behavior in its natural environment. It is somewhat unusual in being both a big-T theory (its abstract superstructure) and a grounded theory (its research guiding part). Among its advantages are conceptual integrity and well defined terminology, readily available empirical confirmation and intertheory connections. We trace its historical origins and evaluate behavior setting theory in terms of its breadth and scope, internal consistency, intertheory connections, and empirical support. We emphasize the fact that, although behavior setting theory has not been widely accepted and implemented in mainstream psychology, it has become a cornerstone of a number of research areas and disciplines like ecological psychology, environment and behavior studies, behavioral ecology, environmental psychology, and sociological social psychology.